Biomechanical analysis of location of lag screw of a dynamic hip screw in treatment of unstable intertrochanteric fracture

Objective: The aim of this study was to assess the most adequate location of a lag screw of a dynamic hip screw in the treatment of an unstable intertrochanteric fracture. Methods: Six pairs of proximal femora obtained from fresh adult cadavers were inflicted with iatrogenic unstable intertrochanteric fractures. Fractures of both sides were stabilized with two different favored locations of a lag screw and tested by a Material Testing System machine with increased loads to evaluate the relative migration of the femoral head. Results: There was significant difference (p < 0.05) with less migration of the femoral head by inferior insertion of a lag screw in the frontal plane and central insertion in the coronal plane. Conclusions: Based on theoretical and experimental considerations, the most adequate location of a lag screw of a dynamic hip screw should be inferior in the frontal plane and central in the coronal plane.